1. Field of the Invention
This invention relates to an end-forming machine comprising a bed, which is provided with a workpiece-gripping means and with at least one headstock, which is guided for a displacement along the axis of the workpiece relative the workpiece-gripping means.
2. Description of the Prior Art
End-forming machine tools are used to center, drill, bore, cut to length, profile or chamfer workpieces, particularly shafts and tubes, and to subject the workpieces to other machining operations at their ends. The workpiece-gripping means grip the workpiece at a distance from the end to be formed so that that end is exposed for the desired forming operation. The forming operation proper has previously been performed only by tools carried by the headstocks, which are known in various forms and can be used as single-spindle or multi-spindle headstocks. Such headstocks may be provided with any of a large number of specific toolholders, which are designed to perform specific or combined machining operations. In spite of the large number of toolholders and tools which can be selected, such forming of ends is not satisfactory because a high expenditure is involved and any attempt to reduce the machining time will be at the expense of the precision and surface finish which can be achieved and of the edge life of the tool. For this reason the steadily increasing requirements regarding shorter machining times, a higher precision and surface finish, and a longer edge life, can be met only with a compromise. It must be borne in mind that the dimensions of the toolholders must be selected in adaptation to the workpieces involved and for surface-finishing operations the cutting circles of the cutting tools employed must lie within a rather small diameter, which will depend on the workpiece diameter. For this reason rather different cutting speeds will be obtained when a plurality of radially offset workpieces, such as required for combined machining operations, are employed. Such different cutting speeds will result in a lower precision and surface finish and in a shorter edge life. On the other hand if a toolholder is used which is provided with only one cutting tool, the precision and the surface finish as well as the edge life can be improved by the selection of proper cutting conditions but a plurality of forming operations will be required, which involve a change of the toolholder or spindle so that the required machining time cannot be reduced.